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Blaise reaction

Type of chemical reaction

Blaise reaction
Summary

Type of chemical reaction

The Blaise reaction is an organic reaction that forms a β-ketoester from the reaction of zinc metal with an α-bromoester and a nitrile. The reaction was first reported by Edmond Blaise (1872–1939) in 1901. The final intermediate is a metaloimine, which is then hydrolyzed to give the desired β-ketoester.

The Blaise reaction

Bulky aliphatic esters tend to give higher yields. Steven Hannick and Yoshito Kishi have developed an improved procedure.

It has been noted that free hydroxyl groups can be tolerated in the course of this reaction, which is surprising for reactions of organometallic halides.

Mechanism

The mechanism of the Blaise reaction involves the formation of an organozinc complex with the bromine alpha to the ester carbonyl. This makes the alpha carbon nucleophilic, allowing it to attack the electrophilic carbon of the nitrile. The negative nitrile nitrogen resulting from this attack complexes with the zinc monobromide cation. The β-enamino ester (tautomer of the imine intermediate pictured above) product is revealed by work-up with 50% K2CO3 aq. If the β-ketoester is the desired product, addition of 1 M hydrochloric acid hydrolyzes the β-enamino ester to turn the enamino into a ketone, forming the β-ketoester.

Blaise Rxn Mechanism

References

  1. Edmond E. Blaise; Compt. Rend. 1901, 132, 478.
  2. Rinehart, K. L., Jr. Organic Syntheses, Coll. Vol. 4, p. 120 (1963); Vol. 35, p. 15 (1955). (Article)
  3. Rao, H. S. P.; Rafi, S.; Padmavathy, K. Tetrahedron 2008, 64, 8037-8043. (Review)
  4. Cason, J.; Rinehart, K. L., Jr.; Thorston, S. D., Jr. J. Org. Chem. 1953, 18, 1594. ()
  5. Hannick, S. M.; Kishi, Y. J. Org. Chem. 1983, 48, 3833. ()
  6. Marko, I.E. J. Am. Chem. Soc. 2007, ASAP
  7. Wang, D.; Yue, J.-M. Synlett 2005, 2077-2079.
Wikipedia Source

This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page.

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